Composite bearing metal



the same time improves the lubricating or bear- My experiments have also shown that the 40 50 added to the composition will have the desired magnesium may, of course, be employed for this 50 UNITEDSTATES PATENT OFFICE 2,114,629 COMPOSITE sesame METAL William E. McCullough, Detroit, Mich, assignor to Bohn Aluminum & Brass Corporation, De-

troit, Mich., a corporation of Michigan No Drawing. Application July 12, 1937,

Serial No. 153,201

4 Claims. (01. 75-163) The invention relates to metal compositions of nesium added to the composition will have the the general type known as copper lead alloys and beneficial effect and will avoid the detrimental which are extensively used in the forming .of effect of the tin. bearings for working parts. It is the object of My improved composition may be manufacthe invention to obtain a composition of this type tured by various methods. In one method prohaving physical characteristics which better ducing satisfactory results a small but definite adapt it for use in bearings, particularly those percentage of magnesium is first alloyed with the designed for heavy duty and high speeds. molten lead which is then cast into ingots. The It has now been well demonstrated that the percentage of magnesium may vary from 0.05% fatigue endurance (resistance to cracking) of the to 5%, this magnesiumbeing readily soluble in leaded bronze lining of steel-backed bearings is the molten lead, and requiring no special pregreater with certain types of metal structure than cautions during melting. The lead-magnesium with others. For instance, when ordinary copalloy is then cast into ingot or other suitable per is melted and commercial lead is added to forms. Copper is then melted, preferably, but the molten copper, it is diflicult to retain more not necessarily, in a crucible type of furnace, 15 than 30% of lead in the cast lining at a point which may be heated in any conventional way. of an inch removed from the steel back, and Commercial pig lead may then be added to the the copper invariably assumes a definite dendritic molten copper to a desired amount, but I prefer form, with lead filling in the spaces between the to add approximately 40% of such ordinary pig branches of the copper dendrites. lead. A further addition of magnesium bearing When such bearings are run in an engine they lead is then made to themolten mixture, sufare subjected to stresses which result in a crackficient to add a small percentage of magnesium ing of the lining and eventually the destruction to the molten metal. My experiments have of the bearing through the cracked pieces loosshown that this amount of magnesium may be as ening from the shell. This is characteristic of varied from .005% by weight to 1% by weight, the failure of the majority of aircraft engine following which the metal is cast into a previbearings, the cracked areas usually occurring at ously heated steel shell in any conventional way. the points of greatest stress. I have discovered I have also found that metallic magnesium that one cause of such failures is the dendritic may be added directly to the molten copper-lead structure of the copper content, which while mixture with apparently the same result, but I holding the lead between dendrites does not suffind it more convenient to control the exact ficiently integrate or hold together all parts of amount of magnesium so added through previthe structure. I have further discovered an imously alloying it with lead, as described. In my proved composition and method of forming the experiments fifty consecutive heats of metal have same, in which the copper forms a substantially been melted and cast, using magnesium additions continuous matrix completely enclosing each over the range previously set forth, with not in a lead globule. Such composition has greatly imsingle instance producing a leaded bronze linproved physical characteristics, particularly in' log having a dendritic structure, the lining being that it lessens the danger of cracking and at invariably of the matrix type.

ing quality of the metal. addition of magnesium may be made through My improved composition is formed by the adthe compression into small tablets of a mixture of dition to the copper and lead of a metallic ele- 90% copper powder and 10% magnesium powder, ment which has a strong modifying action and these tablets being added to'a molten mixture of 4:, prevents a dendritic formation of thecopper concopper and lead just before casting. The cast 5 tent. Various metals may be used for this purmetal after this treatment with the copper-magpose, but not all are desirable because of the nesium composition shows the same non-denother properties of a more or less detrimental dritic character as when the magnesium-lead alcharacter. For instance, a small amount of tin loy is used. Various proportions of copper and result in changing the structure of the copper purpose. It is less convenient, however, to use content, but it is, nevertheless, detrimental in the magnesium in powdered form than in the that it decreases the lubricating characteristic form of lead-magnesium alloy. I have also of the lead with greater danger of seizure. I have added an alloy of /2% magnesium in copper with discovered that a small quantity of metallic magsimilar results.

While -I have described the treatment of the molten copper-lead metal with metallic magnesium, with copper-magnesium compressed from powdered metals, with copper-magnesium alloy, and the treatment with a lead-magnesium alloy, it is obvious that there would be various other methods of treating the metal with magnesium, for instance, with magnesium vapor, etc., but I consider all such other possible methods of treating a molten mixture of copper and lead with magnesium in any form prior to casting in final form would fall within the scope of my discovery.

The magnesium additions have covered a range over the various samples and have shown a residual magnesium in the bearing lining varying from a spectrographic trace up to a chemical content of 0.42% of metallic magnesium, with no basic difference in structural type of the lining although it-appears that the addition of magnesium in the smaller amounts. results in a somewhat finer distribution of the lead throughout the copper matrix. A further benefit from the addition of magnesium has been that the copper retains more lead in the matrix than when tin is used or when no addition agent is used and bearings have been cast with 40% of lead evenly dispersed throughout the matrix at a distance of 3,2: of an inch from the steel shell,

that being the thickness of lining usually employed in such bearings in the finished state.

What I claim as my invention is:

1. A bearing composed of copper, lead, and magnesium in the proportions of not less than 55 per cent by weight of copper nor more than nor less than 20 per cent by weight of lead and from a spectrographic trace to 5.0 per cent by weight of magnesium.

2. A composition of matter composed of from to per cent by weight of copper, from 20 to 45 per cent by weight of lead and from a spectrographic trace to 1.0 per cent by weight of magnesium.

3. A bearing lining for steel-backed internal combustion engine bearings composed of from WILLIAM E. MccULLoUaH. 

